This invention relates to support systems. More particularly, the invention relates to support systems such as mattresses, cushions, upholstery padding and the like which have a liquid in them such as, for example, waterbeds.
Support systems which contain liquids, such as waterbeds and cushions and the various benefits thereof are well-known. On the other hand, such systems exhibit many disadvantages. For example, conventional waterbeds and cushions produce a kind of wave action or rolling motion when in use due to the tendency of the water or other liquid inside the system to rush rapidly from one part thereof to another when an individual places his weight thereon and forces the liquid to flow to another part of the system. Moreover, since the envelope containing the liquid in such a system is typically elastically yieldable, a reaction to the initial liquid surge occurs. This reaction results in a succession of countersurges within the envelope until the system reaches equilibrium. The described undamped surging and countersurging of the liquid in such systems is not only annoying to most individual users of such systems, but actually results in motion sickness in some of them. In order to obviate the above-mentioned disadvantages, many waterbed manufacturers do not employ liquid displacement in that portion of the system which is intended to support the head and shoulders of the user. Instead, they employ a section of mattressing constructed in the usual manner utilizing coil springs or other equivalent non-liquid structures. Obviously, this introduces an element of complexity to the manufacturing processes and, as well, increased costs.
Some manufacturers of waterbeds have attempted to dampen wave motion in various ways. For example, in U.S. Pat. No. 3,585,356 solid particles, such as styrofoam are disposed in the liquid for this purpose, while U.S. Pat. No. 3,600,726 discloses a therapeutic or comfort pad having a flexible film outer envelope filled with a fluid pervious foam material, water or other fluid being introduced thereto through a valve in the envelope. A flotation pad of somewhat similar construction is disclosed in U.S. Pat. No. 3,611,455. On the other hand, U.S. Pat. No. 3,736,604 discloses flap means, as illustrated in FIG. 11 thereof, for this purpose. In U.S. Pat. No. 4,245,361 there is disclosed a waterbed mattress having a sealed liquid enclosure made of a relatively stiff peripheral cushion of foam material having a central cavity which contains a resilient open-cell filling.
A pad having open-cell resilient foam material encased in and bonded to an impervious envelope provided with a valve for communication with the interior of the envelope to permit passage and containment of fluid is disclosed in U.S. Pat. No. 3,872,525 to provide a damped liquid displacement system. Another liquid displacement system is disclosed in U.S. Pat. No. 3,789,442 which shows a low liquid volume, low weight liquid or water pad for use as a mattress in which a lower cellular foamed material flexible pad is partially hollowed out for reception of a flexible material, liquid filled container, an unhollowed portion of the pad being provided for a user's head and upper body, which the liquid container does not rest on. An upper flexible pad of the same cellular foamed material extends across the lower pad. The entire structure described is contained within a flexible water impervious sheath, the structure being inserted through openings in the ends of the sheath which are subsequently closed. Another low-water volume, low-weight water pad for use as a mattress or cushion having a water-filled container sandwiched between upper and lower layers of cellular foam sheets all surrounded with a water impervious sheet is disclosed in U.S. Pat. No. 3,702,484.
U.S. Pat. No. 2,748,399, on the other hand, discloses a light-weight foam rubber cushioning structure in which a bag or chamber having a plurality of compartments, which may either communicate with or be isolated from one another, are filled with air. A layer of foam rubber is supported on the chamber, or the chamber may be sandwiched between two layers of foam rubber. In Swiss Pat. No. 608,951, there is shown a cushion structure which has an air-tight and water-tight inner sheath having a framework of plastic or elastic material, the sheath being filled with a liquid. The inner sheath is subdivided into multiple separate compartments which may be wholly isolated from each other or which may communicate with each other by way of orifaces or valves. The inner sheath is enclosed in an air-tight or water-tight outer casing which has a larger volume than the inner sheath and which also may be filled with a liquid or with air. Finally, U.S. Pat. No. 4,370,768 discloses a damped fluid displacement support system having an envelope of flexible material enclosing a core of resilient liquid-absorbent material which is substantially saturated with a liquid and which envelope may also include an interior divider to separate the envelope into two compartments.
While various of the above-mentioned references provide systems which ameliorate the wave action or rolling motion of the liquid contained therein to some extent in comparison to conventional systems, and while the last-mentioned reference, U.S. Pat. No. 4,370,768, provides a system which achieves such a result to an even greater extent than the others, there still exists a need for a system to overcome to an even greater extent the disadvantageous wave action or rolling motion in such systems.
Another disadvantage exhibited by conventional liquid displacement support systems is that they are relatively unstable in their tendency to react too rapidly in response to the application or shifting of any weight or force on them. For example, when an individual lying on such a system employed as a mattress attempts to roll over, the mattress yields rather quickly under him as he presses against it with one of his limbs to initiate movement. The mattress undulates under him as the liquid surges about within it. Also when the individual attempts to rise from the mattress, he has a strong feeling of instability with respect to his sense of balance or equilibrium, since the mattress rapidly gives way as his weight is shifted to its edge. This instability is also encountered when such liquid displacement support systems are utilized as cushions on a conventional chair, a wheelchair, or on the seat of an automobile. The instability is manifested very clearly in such instances when an individual attempts to rise from a conventional chair or a wheelchair, or to alight from an automobile. What actually occurs is that the liquid is quickly displaced within the cushion as an individual's weight is shifted and he has the feeling that the cushion is squirting out from under him as he attempts to thrust his body upwardly. Furthermore, the normal rocking motion of a moving automobile or wheelchair is greatly amplified by conventional liquid filling cushion systems for the same reasons. Once again, while various of the above-mentioned references provide systems which alleviate this disadvantage, that is the relative instability in response to the application of force or weight thereto, to some extent and U.S. Pat. No. 4,370,368 achieves such a result to an even greater extent than various of the other references discussed above, there still exists the need for a system to overcome this instability to an even greater extent.
Another disadvantage associated with conventional liquid displacement support systems is the requirement of such systems to be utilized for the most part in a horizontal disposition. This is so because if a relatively elongated liquid displacement support system or unit is disposed vertically, or at some considerable angle to the horizontal, the liquid will be drawn by gravity to the lower portions. This causes bulging in these areas while substantially lowering or substantially completely eliminating the cushioning and supporting effects in the upper areas. Consequently, such systems are of only limited usefulness as backrests or upholstery padding or in hospital beds, for example, where a portion of the bed needs to be tilted at an angle to the horizontal. U.S. Pat. No. 4,370,678 recognizes this problem and while it alleviates it to some extent by providing a system in which a reduced amount of liquid is employed, the movement of which is damped and modulated by employing a core of flexible cellular material which is substantially completely saturated by the liquid, there still exists a need for providing liquid displacement support systems which exhibit even greater improvement in this respect no matter what their spatial disposition may be.
A still further disadvantage of conventional liquid displacement support systems resides in the fact that most utilize non-compressible, or at most only slightly compressible liquids, such as water, and they are provided with flat planar surfaces with which the body of a user comes into direct contact. Thus, the skeletal protuberances, particularly those such as the pelvis and hip bones, the coccyx, the spinal vertebra, the shoulder blades, the elbows, the knees and the ankle bones, of the body of an individual using such systems come into direct contact with the planar surfaces thereof. Thus, discomfort results to the user due to the force of the action of such bony protuberances against the planar surfaces of the systems and the consequent force of the reaction of the liquids in such systems to such force. This disadvantage is particularly troublesome in situations where such systems are utilized, for example, as cushions or wheelchairs where an incapacitated individual must remain seated thereon for extended periods of time or in hospital beds where an individual user may have to remain substantially immobile for extended periods or have only limited capacity for movement. The same is also true, however, in situations where the systems are employed as cushions in an automobile and the user must remain in substantially one position for extended periods. While various of the above-mentioned references alleviate this problem somewhat by the utilization of cushioning means, such as foam padding, there still exists the need for systems which obviate this problem to an even greater extent.
A still further disadvantage of conventional liquid displacement support systems is their weight. Since substantially the entire interior of the liquid cell is filled with liquid, its overall weight is considerable. Again, while various of the above-mentioned references overcome this problem to some extent, there still exists a need for systems which further ameliorate this disadvantage to an even greater extent.
From the above discussion it is evident that while liquid displacement support systems have evolved to a point where the many disadvantages of the earlier systems have been overcome to some extent, such systems still exhibit the above-mentioned disadvantages and a need still exists for the provision of liquid displacement support systems which do not exhibit the same. The present invention fulfills this need.